Multilateral well technology allows an operator to drill a parent wellbore, and subsequently drill one or more lateral wellbores that extend from the parent wellbore at desired angular orientations. For many well completions, such as offshore deepwater wells, multiple lateral wellbores are often drilled from a single parent wellbore in an effort to optimize hydrocarbon production while minimizing overall drilling and well completion costs.
Briefly, drilling a multilateral well first requires that the parent wellbore be drilled and at least partially lined with a string of casing or other type of wellbore liner. The casing is subsequently cemented into the wellbore to strengthen the parent wellbore and facilitate isolation of certain areas of the formation for the production of hydrocarbons. A casing exit (alternately referred to as a “window”) is then created in the casing at a predetermined location to initiate the formation of a lateral wellbore. The casing exit can be formed by positioning a whipstock at the predetermined location in the parent wellbore to deflect a mill laterally to penetrate the casing and form the casing exit. A drill bit is then inserted through the casing exit to drill the lateral wellbore to a desired depth, and the lateral wellbore can then be completed as desired.
Selective isolation and/or reentry into each of the lateral wellbores is often necessary to optimize or stimulate production from the associated hydrocarbon producing formations. A typical multilateral well completion will have a reentry window assembly (alternately referred to as a lateral reentry window) installed within the parent wellbore at each lateral wellbore junction. Each reentry window assembly includes a completion sleeve (alternately referred to as a “completion window” or that provides access into the lateral wellbore from the parent wellbore. An isolation sleeve is arranged within the completion sleeve and is selectively movable to cover or expose the casing exit defined through the casing. When it is desired to enter the lateral wellbore, the isolation sleeve is moved axially within the completion sleeve to expose the casing exit and thereby allow access into the lateral wellbore with one or more downhole tools.